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existence of life, whether animal or vegetable, becomes im- 

 possible ; where it is insufficiently supplied, life is proportion- 

 ally enfeebled or repressed. But, to limit our consideration 

 to the vegetable kingdom, it may be observed, that where a 

 loose and deep soil affords an aljundant supply of food, where 

 a genial climate diffuses warmth in an adequate degree, and 

 where a favourable exposure allows a competent access of 

 light (for air, being fully and universally given, may be 

 thrown out of the case ;) in these circumstances, a plant, if 

 not mechanically injured, will vigorously exercise its func- 

 tions, and attain the full development of its parts, thus 

 realizing the absolute complement of life, to which it natu- 

 rally tends. In the same way, when these conditions are 

 stinted, the luxuriance of the plant is checked, in the ratio 

 of that restraint, and the deficiency of the supply. Where 

 any one of the external conditions is partially or inadequately 

 supplied, the plant appears to make special, and even forced 

 efforts to secure as much of the beneficial influence as it can, 

 and to accommodate itself to the exigency of its situation. 

 Thus, where light is admitted only from a single point, a 

 plant concentrates all its powers, in stretching towards the 

 direction of the light. Where light is shed all around, the 

 plant throws out its branches on every side. In conformity 

 with this principle, we find, that, in the interior of a wood, 

 where the trees mutually impede the lateral admission of 

 light, the tendency of each is upwards ; and the consequence 

 of this tendency is, that the plant is thereby not developed 

 in its natural and perfect proportions, but is elongated, or 

 drawn up to an undue height. It displays its ramification 

 chiefly near the top ; while the imperfection of its life is 

 manifested, in the whole character of its vegetation. In open 

 exposures, on the other hand, the tree developes its existence. 

 in full health and luxuriance. It reaches a height, such as 

 the soil and situation admit, and sufficient to allow the 

 branches, which are thrown out on every side, to expand 



